Apparatus for rapidly accelerating and cushionably decelerating a piston-like member

ABSTRACT

By way of illustration, the apparatus may be used to launch rather heavy, spherical objects from a travelling space vehicle. In this event, the piston cradles the sphere and is driven by a high-thrust, short duration-time rocket motor. At launching velocity snubber assemblies arrest the piston with a minimum of recoil. The snubbers include rods secured to the piston for free travel with it until launching velocity is reached. At that point, the rods engage snubber pistons which are arrested by honeycomb cylinders.

United States Patent [191 Reed [ APPARATUS FOR RAPmLY ACCELERATING ANDCUSHIONABLY DECELERATING A PISTON-LIKE MEMBER [75] Inventor: Wilbur B.Reed, Cambell, Calif.

[73] Assignee: The United States of America as represented by theSecretary of the Navy, Washington, D.C.

22 Filed: Sept. 5, 12m

21 App1.No.:285,961

52 user 8911.5 R, 89/].806, 244/137R 51 Int cr ..r41rs/02 [58] Field ofSearch... 89/1.5, 1, 1.806, 145 B, 1 B; 244/137; 188/1 C [56] ReferencesCited UNITED STATES PATENTS 2,736,236 2/1956 Martin 89/1 B 3,270,6189/1966 Stott 89/1 R X 1 Mar. 5, 1974 3,218,849 11/1965 Marvinney et89/].806 X 3,228,492 1/1966 Blumrich 188/1 C 3,400,661 9/1968 Coon et al89/145 B Primary Examiner-Samuel W. Engle Attorney, Agent, or FirmR. S.Sciascia; P. N.

Critchlow [5 7 ABSTRACT By way of illustration, the apparatus may beused to launch rather heavy, spherical objects from a travelling spacevehicle. In this event, the piston cradles the sphere and is driven by ahigh-thrust, short durationtime rocket motor. At launching velocitysnubber assemblies arrest the piston with a minimum of recoil. Thesnubbers include rods secured to the piston for free travel with ituntil launching velocity is reached. At that point, the rods engagesnubber pistons which are arrested by honeycomb cylinders.

10 Claims, 3 Drawing Figures APPARATUS FOR RAPIDLY ACCELERATING ANDCUSHIONABLY DECELERATING A PISTON-LIKE MEMBER BACKGROUND OF THEINVENTION The present invention relates to energy absorbers capable ofarresting high speed pistons with a minimum of reaction forces.

The principles of the invention can be illustrated by considering itsuse in absorbing the kinetic energy generated by a piston driven at ahigh speed sufficient to launch a relatively heavy object. Inparticular, one of the principal, uses is its incorporation in a spacevehicle to launch heavy spheres into space without appreciably affectingthe flight of the craft or missile. Such spheres are launched for avariety of purposes including optical experiments, electromagnetictransmissions, or the expulsion of chemicals, vapors or other objects toobtain scientific data. One particular launcher, for example, wasdesigned to meet such pre-set conditions as the ability to launch a 195pound, fifteen inch sphere at a launch velocity of 5068 feet per secondwhile the space vehicle was being accelerated to about 9-g, the launchtaking place at an altitude of 250 KFT and in a direction perpendicularto the line of flight. Lateral loads generated by the launch were not toexceed 7,000 pounds and, of course, the launch was to be clean in thatno debris or space junk was generated and the surfaces of the vehicleand craft were not contaminated by the launch.

With these rather restrictive requirements, the use of conventionallaunchers appeared to be eliminated. Other launching devices, such asmechanical springs, gas generators, or nitrogen storage bottles,presented serious problems involving complexity, excessive cost orsimply the fact that they would not work in a reliable manner. Also,space and weight considerations presented critical problems whichobviously would increase as the mass and ejection velocity of the launchincreased.

Consequently, one of the objects of the present inventive effort was toprovide a sphere launcher capable of meeting the foregoing requirements.

A more generalized object of the invention has been to provide apparatusfor rapidly absorbing the thrust force of a travelling piston, theabsorption being accomplished with a minimum generation of reaction orrecoil forces.

Another object was to provide energy-absorbing apparatus capable ofpermitting a working piston to freely and rapidly accelerate to amaximum velocity prior to the initiation of the energy absorption.

A further object was to provide an accelerating force which has ashort-duration burn or thrust time and which is highly predictable tothe extent that a particular thrust level is reached in a designed timeinterval permitting the maximum thrust to be developed and then quicklycut-off prior to the energy absorption phase of the operation.

Another object was provide a cushioning means having repeatableload/deflection characteristics.

Other objects and their attendant advantages will become apparent in theensuing description.

BRIEF DESCRIPTION OF THE DRAWING A preferred embodiment of the presentinvention is illustrated in the accompanying drawings of which:

FIG. 1 is a partial sectional view showing the overall arrangement of asphere launcher;

FIG. 2 is a partial sectional view of one of the tw snubber assembliesemployed to absorb the kinetic energy buildup of the sphere launcher,and

FIG. 3 shows load/deflection curves for a honeycomb cylinder employed toabsorb the energy buildup of the launch.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, theillustrated apparatus is intended to launch a 15 inch sphere l cradledin the forward end of a launcher piston 2 that is driven by a highthrust, rocket-type motor 3 carried by the launcher piston. Snubberassemblies 4, decelerate the piston and cushion or absorb the kineticenergy buildup when the piston is accelerated to launching velocity. Atension stud arrangement 6 securely holds the sphere in itspiston-cradled position and, of at least equal significance, it alsoinitially restrains piston 2 until the motor attains a predeterminedthrust level. Each of these individual major components subsequentlywill be described in greater detail.

As shown in FIG. 1, all of the components are contained within alauncher barrel 7 which is a smoothbore, semi-rigid, rib reinforcedstructure machined from a forged aluminum cylinder, this particularbarrel being approximately 26.2 inches long with an inside diameter ofl6 inches and a nominal wall thickness of- 0.l56 inches. Preferably, the16 inch id. is hard anodized and coated with a film of baked-on drylubricant. Its supporting structure includes two longitudinal aluminumchannels 8 and 9 secured to each other and to the barrel by twotransverse aluminum channels 11 and 12. The lower flanges of thechannels provide a mounting interface with the parent vehicle, which, inthis instance, may be considered as the previouslydescribed spacevehicle. As already stated, it is preferred that the launching directionbe perpendicular to the vehicles longitudinal axis and, to achieve thisresult, launcher barrel 7 may be mounted transversely of the spacevehicle, the vehicle itself being provided with two doors, both of whichare open at the time of the launch. Launching, of course, isaccomplished by expelling the sphere through one of the open doors whilethe other door is open. Rocket motors presently are preferred for usewith space vehicles since their thrust is very predictable and sincefiring of these motors under vacuum conditions has little recoil orreaction. A space vehicle such as the one presently contemplatedoperates in vacuum conditions. However, other power sources arecontemplated and may be found equally suitable particularly inapplications not directly concerned with space flight.

Launcher piston 2 cradles and supports the sphere during both thelaunching and flying of the vehicle and the launching of the sphere. Asshown, the piston has a cup-shaped forward portion provided with aninterior hemispherical surface machined to the same contour as sphere 1.Preferably, it is fabricated from an aluminum forging provided on itscup-shaped interior surface with a dry film lubricant. The outsidesurface also may be hard anodized and provided with a dry film lubricantto reduce friction loss. The aft face of the forward end of the pistonis rib reinforced in the manner shown in FIG. 1, the ribs providing amounting surface for the attachment of rocket motor 3. lnteriorally, itscup-shaped face mounts a l.5 inch diameter steel index pin 13 whichengages the sphere to remove any rotational momerits induced by thevehicle launch or the flight dynamics.

Rocket motor 3 is a Foilac motor approximately 6.75 inches in diameterby inches long and weighing 14.5 pounds. The propellant can be varied tomeet different thrust requirements and, in a conventional manner,ignition of the motor can be accomplished by a standard low-voltagesquib (not shown). One suitable motor, for example, builds up a thrustforce of approximately 6,000 pounds and, of particular importance, thismotor, or any other which may be employed, should be of a type having ashort-duration time interval between ignition and burn out. For reasonswhich will become apparent, proper operation of the apparatus requiresthat the burn-out time interval be precise and predictable, preferablywithin a matter of milliseconds.

Absorption of the thrust energy is accomplished by special snubberassemblies 4., there being two such assemblies bolted to the insideoflauncher barrel 7 about 180 apart. Referring to FIG. 2. each assemblyincludes a housing M provided with a cylindrical bore in which ismounted a snubber piston 16 that also is provided with an internal borein which a snubber rod 17 is reciprocably mounted. Snubber rod 17'extends the full length of the bore of the snubber piston and has an endportion 18 projecting through the forward end wall of the snubber pistoninto a secure engagement with launcher piston 2. To accommodate theengagement, launcher piston 2 is formed with a projecting boss portion19 having an opening through which projecting end portion 18 of thesnubber rod extends, the end of the snubber rod being threaded toreceive a fastening nut 21. Obviously, as launcher piston 2 is drivenfor wardly, snubber rod 17 is carried along by its piston engagement.The trailing or rearward end of snubber rod 17, however, mounts aradially enlarged cork bumper 22 which, when snubber rod 17 has reachedthe end of its forward stroke, engages with end flanges 23 of thesnubber piston to driveably couple the snubber piston with launcherpiston 2.

The coupling of launcher piston 2 with snubber piston to causes thesnubber piston to move forwardly and it is the forward movement of thesnubber piston that is cushioned for the purpose of absorbing thekinetic energy generated by the motor and the loadcarrying launcherpiston. For this purpose, a honeycomb cylinder Zd is mounted in atrapped position within snubber housing 141. Thus, as will be seen,honeycomb cylinder 24 is trapped at one of its ends by inwardlyextending end wall 26 of housing 14 and its other end by a radiallyextending flange 27 carried by snubber piston 16. The forward movementof snubber piston 16 causes the force applied to launcher piston 2 to betranslated through flanges 27 to honeycomb cylinder 24 to completelyabsorb these forces in a rapid and predictable manner. Snubber piston16, as will be seen, is retained within the bore of housing 14 by an endwall retainer ring 28 which engages flange 27 when the snubber piston isin its rearward disposition.

Honeycomb cylinder 24 is a hollow cylindrical member formed, forexample, of 5052 aluminum having one-fourth inch hexagonal cells. Theproperties of the honeycomb however, may vary for different purposes,these properties, such as foil gage, adhesive and cell size establishingthe honeycomb density which provides the load/deflection capability ofthe composite. Preferably, about 73 percent of the honeycomb tube-coreis useable as a stopping distance. pre-crushing the honeycomb one-eighthof an inch eliminates a load spike which otherwise is an undesirablecharacteristic. Thus, FIG. 3 shows a typical crush curve which comparesthe honeycomb load displacement of a pre-crushed tubecore with a corethat has not been pre-crushed. A typical initial spike load appears inthe curve for the uncrushed honeycomb, while the curve for theprecrushed honeycomb has no similar spike. The average crush distanceshown is the distance required to stop a 32 pound piston and a burnt-outrocket motor of the type which has been described. Precrushed honeycombtube-core fabricated in this form is found to have very repeatableload/deflection characteristics. Also, the radial clearance for thehoneycomb cylinder should be sufficient to eliminate friction during thecrush stroke. Under vacuum conditions, the dynamic load/deflection curveremains essentially the same as the static load/deflection curve. Atambient conditions, however, the load carrying capability of thehoneycomb under dynamic loading is increased over the staticload/deflection curve due to entrapped air. V enting arrangements can beprovided as needed.

Tension stud assemblies 6 are provided to retain launcher piston 2 andits sphere l in a retracted position until the rocket motor has built upits desired thrust level which, as stated, may be about 6,000 pounds.For this purpose, each of the assemblies includes a pyramidal-shapedlauncher bracket 31 preferably machined from an aluminum bar and boltedto the inside of launcher barrel 7 about 180 apart so that, in effect,they are located about from each of the two snubber housings 114.Tension studs 32 used in the assemblies may be fabricated from steel rodthreaded at both ends. As shown, these studs are carried by thebrackets, the rearward end of the stud being received in a suitableopening or clearance hole provided in the bracket. The rearward threadedend of each stud is secured by a nut and washer assembly 33, while thefor ward portion extends through a boss-like flange 34 carried bylauncher piston 2 and through an opening in the wall of the launcherpiston into a threaded engagement with inserts 36 provided in thesurface of sphere 1.

Another feature of considerable significance is the fact that each ofthe tension studs is formed near its sphere interface with a reduceddiameter fracture groove 37 which permits the tension studs to fractureat a particular load which, in the present embodiment, may be a load or"about 3,000 pounds. As will be recalled, the presently-contemplatedrocket motor generates a thrust that builds up to approximately 6,000pounds. At this thrust level the two tension studs fracture allowing themotor to rapidly accelerate the launcher piston and its sphere loadalong the barrel. Since these tension studs function as locking andrelease elements for the sphere, the fracture grooves should be machinedto close tolerances. Preferably, the rods are heat-treated to obtainproper physical charac teristics. Aside from the locking and releasefunction ing of the tension assemblies, it should be noted that thebrackets of the assemblies serve as an anchor or tiedown member to clampthe sphere and the sphere piston to the inside of the launcher barrel.Thus, the brackets transmit the applied loads through the barrelassembly into the structure during the vehicle launch dynamics andduring the subsequent motor thrust buildup to the point of tension studfracture.

OPERATION With a launcher assembled as shown in FIG. 1, rocket motor 3is squib-ignited. Due to the clamping action of tension assemblies 6,the thrust of the motor is permitted to build up to about 6,000 poundsat which point tension studs 32 fracture allowing the thrust of themotor to accelerate the sphere and launcher piston 2 along the barrel.As will be apparent, the sphere and piston can accelerate in a free,unrestrained manner since snubber rods 17 of the snubber assemblies arepermitted to move freely through the inside bore of snubber piston 16.The extent or stroke of the free travel of the snubber rods is dependentupon the dimensions of the assembly. For example, the snubber rod may bepermitted to travel freely approximately through a inch forward stroke,the time interval required for this stroke permitting rocket motor 3 todevelop full thrust and bum-out. Milliseconds after thrust terminationor burn-out, cork bumper 22 mounted on the trailing end of each snubberrod engages with inner end walls 23 of the snubber piston to driveablycouple the snubber piston to the forward movement of launcher piston 2.The coupling of the two pistons commences the deceleration andcushioning of launcher piston 2 to absorb the kinetic energy that hasbuilt up. The deceleration force is transmitted aft along snubber piston16 to its rear flange 17 which is in contact with the pre-crushed end ofhoneycomb cylinder 24. At the start of deceleration, the sphereseparates and is ejected from this piston and the energy remaining inthe piston and the burnt-out motor is absorbed by further crushing thehoneycomb cylinders.

Sphere launchers of the type described have been subjected to a numberof environmental and flight simulation tests including successful spherelaunchings under about lO-g acceleration. The test data indicated asphere ejection at an average velocity of 56-58 feet per second andlateral loads well within the allowable 7,000 pounds which, it will berecalled, was one of the predesign requirements. The actual maximum loadrecorded at tension stud fracture was 6,375 pounds. The maximumdeceleration load recording during honeycomb crush was 5,500 pounds. Ingeneral, as indicated, this launcher has successfully satisfied all ofthe requirements of the flight objective. Thus, relatively heavy objectscan be ejected at moderate velocities with a minimum of reaction forces.Obviously, within limits, this system can be scaled up or down to meetparticular requirements and the mechanics of the modifications shouldinvolve relatively simple calculations. The use of the honeycomb, ofcourse, is a one-shot application, although other launcher hardware isreuseable if it can be recovered.

As now should be apparent, the present snubbing principles areconsidered applicable to a relatively wide range of applications otherthan its special use in space sphere launching. Thus, its advantagesextend to any application requiring a rapid initial acceleration of apiston followed, in a closely timed sequence, by a rapid and completedeceleration and absorption of the generated kinetic energy.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

I claim:

1. Apparatus for accelerating a piston-like member to a desiredforwardly-travelling velocity and for rapidly decelerating it from saidvelocity, comprising:

a housing,

a piston-like member slideably mounted in said housthrust means forrapidly accelerating said slidablymounted member to said velocity and;

snubber-like means for decelerating said slidably accelerated memberwithin said housing, said decelerating means including:

a fixed cylinder carried by said housing,

an elongate snubber piston mounted in said cylinder for movement in aforward direction, said piston being formed with an elongate centralbore and with a flange portion extending radially outwardly of its rearportion a snubber rod slideably mounted in said snubber piston bore,

said rod being secured to said piston-like member for travelling in afreely slidable forward stroke in said bore a predetermined distancewith said member and the rod having means for driveably coupling saidsnubber piston at the end of said freely slidable forward stroke, and

cushioning means disposed in said cylinder in the forward path of travelof said snubber piston radial flange portion for decelerating thepiston-like member,

said freely movable snubber rod permitting said piston-like member tofreely reach said desired velocity prior to said deceleration and saidcushioning means directly and initially absorbing the full kineticenergy of said forwardly travelling piston-like member whereby recoilforces are reduced to a minimum.

2. The apparatus of claim 1 wherein said thrust means is of a typehaving a short-duration time thrust force, said duration time beingcorrelated with the time required for said forward stroke of the snubberrod whereby said thrust force terminates immediately prior to thedeceleration of the snubber piston.

3. The apparatus of claim 2 further including;

means releasably securing said piston-like member in a fixed positionuntil said thrust means develops a predetermined thrust force.

4. The apparatus of claim 3 wherein said thrust means is a high-thrustrocket-type motor having a short duration burn time.

5. The apparatus of claim 4 wherein said cushioning means is in the formof a honeycomb cylinder adapted to crushably decelerate said snubberpiston.

6. Apparatus for launching a heavy object from a flying vehicle,comprising:

a housing carried by said vehicle,

a launcher piston adapted to releasably carry said object into launchingposition, said piston being slideably mounted in said housing,

thrust means for accelerating said launcher piston to a desiredforwardly travelling launching velocity,

and

snubber-like decelerating means for rapidly absorbing said forwardthrust, said decelerating means including:

a cylinder carried by said housing,

an elongate snubber piston mounted in said cylinder for movement in aforward direction,

said piston being formed with an elongate central bore and with a flangeportion extending radially outwardly of its rear portion,

a snubber rod slideably mounted in said snubber piston and secured tosaid launcher piston for freely travelling in a forward stroke apredetermined distance with said launcher piston, said rod having meansdriveably coupling said snubber piston at the end of said stroke, and

cushioning means disposed in said cylinder in the forward path of travelof said snubber radial flange portion for decelerating said launcherpiston,

said freely movable snubber rod permitting said launcher piston to reachsaid desired velocity prior to said deceleration and said cushioningmeans directly and initially absorbing the full kinetic energy of saidforwardly travelling piston-like member whereby recoil forces arereduced to a minimum.

7. The apparatus of claim 6 wherein said thrust means is of a typehaving a short duration thrust time, said duration time being correlatedwith the time required for said snubber rod forward stroke whereby saidthrust force terminates immediately prior to the deceleration of thesnubber piston.

8. The apparatus of claim 7 further including;

means releaseably securing said launcher piston in a fixed positionuntil said thrust means develops a predetermined thrust force.

9. The apparatus of claim 8 wherein said thrust means is in the form ofa high-thrust rocket-type motor having a short duration time, said motorbeing carried by said launcher piston.

10. The apparatus of claim 9 wherein said cushioning means is in theform of a honeycomb cylinder adapted to crushably decelerate saidsnubber piston.

1. Apparatus for accelerating a piston-like member to a desiredforwardly-travelling velocity and for rapidly decelerating it from saidvelocity, comprising: a housing, a piston-like member slideably mountedin said housing thrust means for rapidly accelerating saidslidably-mounted member to said velocity and; snubber-like means fordecelerating said slidably accelerated member within said housing, saiddecelerating means including: a fixed cylinder carried by said housing,an elongate snubber piston mounted in said cylinder for movement in aforward direction, said piston being formed with an elongate centralbore and with a flange portion extending radially outwardly of its rearportion a snubber rod slideably mounted in said snubber piston bore,said rod being secured to said piston-like member for travelling in afreely slidable forward stroke in said bore a predetermined distancewith said member and the rod having means for driveably coupling saidsnubber piston at the end of said freely slidable forward stroke, andcushioning means disposed in said cylinder in the forward path of travelof said snubber piston radial flange portion for decelerating thepiston-like member, said freely movable snubber rod permitting saidpiston-like member to freely reach said desired velocity prior to saiddeceleration and said cushioning means directly and initially absorbingthe full kinetiC energy of said forwardly travelling piston-like memberwhereby recoil forces are reduced to a minimum.
 2. The apparatus ofclaim 1 wherein said thrust means is of a type having a short-durationtime thrust force, said duration time being correlated with the timerequired for said forward stroke of the snubber rod whereby said thrustforce terminates immediately prior to the deceleration of the snubberpiston.
 3. The apparatus of claim 2 further including; means releasablysecuring said piston-like member in a fixed position until said thrustmeans develops a predetermined thrust force.
 4. The apparatus of claim 3wherein said thrust means is a high-thrust rocket-type motor having ashort duration burn time.
 5. The apparatus of claim 4 wherein saidcushioning means is in the form of a honeycomb cylinder adapted tocrushably decelerate said snubber piston.
 6. Apparatus for launching aheavy object from a flying vehicle, comprising: a housing carried bysaid vehicle, a launcher piston adapted to releasably carry said objectinto launching position, said piston being slideably mounted in saidhousing, thrust means for accelerating said launcher piston to a desiredforwardly travelling launching velocity, and snubber-like deceleratingmeans for rapidly absorbing said forward thrust, said decelerating meansincluding: a cylinder carried by said housing, an elongate snubberpiston mounted in said cylinder for movement in a forward direction,said piston being formed with an elongate central bore and with a flangeportion extending radially outwardly of its rear portion, a snubber rodslideably mounted in said snubber piston and secured to said launcherpiston for freely travelling in a forward stroke a predetermineddistance with said launcher piston, said rod having means driveablycoupling said snubber piston at the end of said stroke, and cushioningmeans disposed in said cylinder in the forward path of travel of saidsnubber radial flange portion for decelerating said launcher piston,said freely movable snubber rod permitting said launcher piston to reachsaid desired velocity prior to said deceleration and said cushioningmeans directly and initially absorbing the full kinetic energy of saidforwardly travelling piston-like member whereby recoil forces arereduced to a minimum.
 7. The apparatus of claim 6 wherein said thrustmeans is of a type having a short duration thrust time, said durationtime being correlated with the time required for said snubber rodforward stroke whereby said thrust force terminates immediately prior tothe deceleration of the snubber piston.
 8. The apparatus of claim 7further including; means releaseably securing said launcher piston in afixed position until said thrust means develops a predetermined thrustforce.
 9. The apparatus of claim 8 wherein said thrust means is in theform of a high-thrust rocket-type motor having a short duration time,said motor being carried by said launcher piston.
 10. The apparatus ofclaim 9 wherein said cushioning means is in the form of a honeycombcylinder adapted to crushably decelerate said snubber piston.